Problem: Expand and combine like terms. $(5a^3-2)(5a^3+2)=$
Explanation: We can expand this expression like any product of two binomials. However, this expression has a special form that makes it easier to expand. This is the "difference of squares" form (where $P$ and $Q$ can be any monomial): $(P+Q)(P-Q)=P^2-Q^2$ $\begin{aligned} &\phantom{=}(5a^3-2)(5a^3+2) \\\\ &=\left(5a^3\right)^2-(2)^2 \\\\ &=25a^6-4 \end{aligned}$